Unsteady Aerodynamic Characteristics and Safety of High-speed Trains under Crosswinds

In order to study the unsteady aerodynamic characteristics and safety of high-speed trains running in different road conditions (ground, embankment, viaduct) under crosswinds, an aerodynamic model and a vehicle system dynamic model of the high-speed trains are established based on the theories of aerodynamics and multi-body system dynamics. Using Detached Eddy Simulation method, the flow fields around high-speed trains with the running speed of 300 km/h under crosswinds are simulated, the wind speeds are 17.1 m/s, and the directions of winds are vertical to the running directions of trains. The characteristics of the unsteady aerodynamic forces acting on the trains in different road conditions are presented from the numerical results, which include the characteristics of the time domain, the frequency domain, and the unsteady flow structures around the trains. Then, according to the standard of testing of high-speed electric multiple unit on completion of construction, the operational safety of trains running in different road conditions are analyzed using the operational safety indicators of the derailment coefficient, the load reduction rate, the axle lateral force, and the wheel-rail vertical force. The results show that the aerodynamic loads on trains under crosswinds have strong unsteady characteristics and the power spectrum densities of the aerodynamic loads of each vehicle have obvious peak values. The dominant frequencies of the aerodynamic loads concentrated within 5 Hz. The safety of the train running in the leeward of double-track embankment is worst, followed by the windward of double-track viaduct, the leeward of double-track viaduct, the windward of double-track embankment, ground.